Seatbelt retractor

ABSTRACT

A side wall portion of a housing is provided with an arm-protective extending portion below a pawl and a mechanical arm. The arm-protective extending portion extends inwardly at a substantially right angle. Further, a side wall portion of the housing is provided with a shaft-protective extending portion which extends inwardly from the lower edge portion of a horizontally long opening portion. The horizontally long opening portion is formed so as to face a coupling shaft over its full length. Below this shaft-protective extending portion, there is formed a bolt insertion hole through which a bolt is inserted at the time of mounting the housing to a fastening piece of a vehicle.

TECHNICAL FIELD

The present invention relates to a seatbelt retractor which removes theslack of webbing in case of an emergency such as vehicle collision orthe like.

BACKGROUND ART

Conventionally, a seatbelt retractor for the front seat of a vehicle ishoused inside a center pillar from an opening portion formed in a lowerportion of an inner panel of the center pillar, and thereby mounted to avehicle body. For instance, as disclosed in Japanese Laid-open PatentPublication No. 2006-315572 (paragraphs 0015-0034, FIG. 1-FIG. 7), afastening piece protruding upward is provided at the center position ofthe lower edge portion of an opening portion formed in the lower portionof an inner panel of a center pillar. Additionally, a screw hole isformed in the vicinity of the center position in the upper edge portionof this opening portion. The lower end portion of a base plate of theseatbelt retractor is fastened to the upper end portion of the fasteningpiece with a bolt and nut. The upper end portion of this base plate isfastened with a bolt and nut at the screw hole formed in the centerposition in the upper edge portion of the opening portion through amounting plate member having a crank shape in cross section and formedso as to overhang the outside of the vehicle.

DISCLOSURE OF THE INVENTION

However, in the seatbelt retractor disclosed in the above-describedpatent publication, when a mechanical member is in the vicinity of theinner lower end portion of the base plate of the seatbelt retractor, atthe time of mounting the base plate to the fastening piece protrudingupward, the mechanical member may be brought into contact with thisfastening piece and thereby cause damage to the seatbelt retractor.Furthermore, the mounting needs to be carried out with care so as toavoid contact between the fastening piece and the mechanical member.This makes it difficult to shorten the time required for the work ofmounting.

The present invention has been made in view of the above-describedproblems and an object thereof is to provide a seatbelt retractor whichcan be mounted to a vehicle easily and has a high reliability.

The seatbelt retractor of the present invention which achieves theabove-described object comprises: a take-up drum onto which a webbing iswound and housed; a housing which includes a first side wall portion anda second side wall portion facing the first side wall portion, androtatably supports the take-up drum in between the first side wallportion and the second side wall portion; and a pretensioner assemblywhich rotates the take-up drum in a retracting direction to retract thewebbing in case of vehicle collision. In such seatbelt retractor, thepretensioner mechanism includes a driving device which is mounted to anoutside of the first side wall portion of the housing and causes thetake-up drum to rotate in the retracting direction of the webbing incase of the vehicle collision. The take-up drum includes: a ratchet gearformed on a periphery of an edge portion of the take-up drum which so asto face an inside of the second side wall portion of the housing; a pawlarranged at a position where the pawl is disengaged from the ratchetgear while one end of the pawl is rotatably supported at the inside ofthe second side wall portion of the housing; and a locking device whichis directly activated by the driving device upon activation of thedriving device and locks the pawl in an engaged state with the ratchetgear. The locking device includes: an arm member one end of which isrotatably supported at an outside of the first side wall portion of thehousing; a rotating device which is provided at the outside of the firstwall portion of the housing and is directly activated by the drivingdevice so as to cause the arm member to rotate in a predetermineddirection; a depressing member which is in contact with the pawl at oneside face which is opposed to other side face thereof which is closer tothe ratchet gear while one end of the depressing member is rotatablysupported at the inside of the second wall portion of the housing; and acoupling shaft which couples the arm member and the depressing member.The housing includes: a third wall portion which is opposed to aperiphery of the coupling shaft; a bolt insertion hole which is formedin an opposite end portion of the third wall portion with respect to theretracting direction of the webbing, the bolt insertion hole beingprovided for mounting the housing to a vehicle; a first extendingportion for protecting the shaft which extends from the inside of thethird wall portion so as to be opposed to a side of the coupling shaftwhich is closer to the bolt insertion hole.

In such a seatbelt retractor, the bolt insertion hole is formed in theend portion of the third side wall portion which is opposed to theperiphery of the coupling shaft so as to mount the housing to thevehicle therethrough. Further, the first extending portion forprotecting the shaft extends from the inside of the third side wallportion so as to face the bolt insertion hole side of the couplingshaft.

Accordingly, when fastening the bolt insertion hole formed in the endportion of the third side wall portion to the upper end portion of thefastening piece in the opening portion formed in the lower portion orthe like of the center pillar with a bolt and nut, the first extendingportion for protecting the shaft can prevent contact between thefastening piece and the coupling shaft. This makes it possible to mounta seatbelt retractor to a vehicle easily. At the same time, it ispossible to assuredly prevent damage such as bending of the couplingshaft when mounting to a vehicle, to thereby provide a seatbeltretractor with high reliability.

Further, if the driving device of the pretensioner assembly isactivated, this driving device directly activates the rotating devicewhich rotates the arm member arranged at the outside of the first sidewall portion of the housing in a predetermined direction. Therefore,substantially at the same time as the activation of the driving device,it is possible to directly activate the pawl arranged at the inside ofthe second side wall portion of the housing through the arm member, thecoupling shaft and the depressing member and lock this pawl in theengaged state with the ratchet gear rapidly and reliably.

Further, in the seatbelt retractor of the present invention, the housingpreferably includes a second extending portion for protecting thedepressing member which extends from the inside of the second side wallportion of the housing so as to protect one side face of the depressingmember which is opposed to other side face thereof which is closer tothe pawl.

Further, in such a seatbelt retractor, the second extending portion forprotecting the depressing member extends from the inside of the secondside wall portion of the housing so as to protect one side face of thedepressing member which is opposed to other side face thereof which iscloser to the pawl, the depressing member being arranged at the insideof the second wall portion. Thus, when fastening the bolt insertion holeformed in the end portion of the third side wall portion opposed to theperiphery of the coupling shaft to the upper end portion of thefastening piece in the opening portion formed in the lower portion orthe like of the center pillar with a bolt and nut, it is possible toprevent contact between the fastening piece and the depressing member.This makes it possible to mount a seatbelt retractor to a vehicleeasily. At the same time, it is possible to assuredly prevent damage ofthe depressing member when mounting to a vehicle, to thereby provide aseatbelt retractor with higher reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an outer appearance of a seatbeltretractor according to a present embodiment;

FIG. 2 is a perspective view showing respective assemblies of theseatbelt retractor in a disassembled state;

FIG. 3 is a perspective view of a take-up drum unit;

FIG. 4 is a cross-section view of the seatbelt retractor;

FIG. 5 is an exploded perspective view of the take-up drum unit, apretensioner unit and a take-up spring unit;

FIG. 6 is a perspective view of a pretensioner unit as seen from ahousing unit mounting side thereof;

FIG. 7 is a side view showing the pretensioner unit;

FIG. 8 is an exploded perspective view showing the pretensioner unit inFIG. 6 in a disassembled state;

FIG. 9 is an exploded perspective view of a housing unit;

FIG. 10 is a side view showing the seatbelt retractor with the lockingunit removed therefrom;

FIG. 11 is an explanatory diagram showing a state that a piston is movedin response to the activation of a gas generating member of thepretensioner mechanism and the lower end portion of a rotating lever isdisengaged from the tip end portion of a gear-side arm; and

FIG. 12 is an explanatory diagram showing a pawl operation correspondingto FIG. 11.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, one embodiment of the seatbelt retractor according to thepresent invention will be described in detail while referring to theaccompanying drawings.

[Schematic Configuration]

First, a schematic configuration of a seatbelt retractor 1 according tothe present embodiment will be described based on FIG. 1 and FIG. 2.

FIG. 1 is a perspective view showing an outer appearance of a seatbeltretractor 1 according to the present embodiment. FIG. 2 is a perspectiveview showing the respective assemblies of the seatbelt retractor 1 in adisassembled state.

As shown in FIG. 1 and FIG. 2, the seatbelt retractor 1 is a device forretracting a vehicle webbing 3. The seatbelt retractor 1 is comprised ofa housing unit 5, a take-up drum unit 6, a pretensioner unit 7, atake-up spring unit 8 and a locking unit 9.

The locking unit 9 is fixed to a side wall portion 12 of a housing 11constituting the housing unit 5 as will be described later. The lockingunit 9 carries out an actuating operation to stop pull out of thewebbing 3 in response to a sudden pull out of the webbing 3 or more thanpredetermined acceleration of a vehicle speed. The pretensioner unit 7having a pretensioner mechanism 17 (refer to FIG. 6) as will bedescribed later is mounted to the housing unit 5. To be more specific,the housing unit 5 has a substantially U-shape in plain view and has aside wall portion 13 and a side wall portion 14 which constituteopposite sides thereof. From the top and lower edge portions of the sidewall portions 13 and 14, screwed portions 13A, 13B and screwed portion14A, 14B extend inwardly from each side wall portion 13 and 14 roughlyat right angle and form a screw hole separately. The pretensioner unit 7and the housing unit 5 are screwed with three screws 15 and a stopperscrew 16 at the screwed portions 13A, 13B, 14A, and 14B. Thereby, thepretensioner unit 7 constitutes the other side wall portion opposite theside wall portion 12 of the housing 11.

A take-up spring unit 8 is fixed to an outer side of the pretensionerunit 7 by nylon latches 8A which are integrally formed with a springcase 56 (refer to FIG. 5).

A take-up drum unit 6 onto which the webbing 3 is wound is rotatablysupported between the pretensioner unit 7 and the locking unit 9 fixedto the side wall portion 12 of the housing unit 5.

[Schematic Configuration of Take-Up Drum Unit]

Next, a schematic configuration of the take-up drum unit 6 will bedescribed based on FIG. 2 through FIG. 5.

FIG. 3 is a perspective view of a take-up drum unit 6. FIG. 4 is across-section view of a seatbelt retractor 1. FIG. 5 is an explodedperspective view of the take-up drum unit 6, the pretensioner unit 7 andthe take-up spring unit 8.

As shown in FIG. 2 through FIG. 5, the take-up drum unit 6 is comprisedof a guiding drum 21, a drum shaft 22, a torsion bar 23, a wire 24, awire plate 25, a ratchet gear 26 and a bearing 32.

The guiding drum 21 is made of an aluminum material or the like and isformed in a substantially cylindrical shape, with one end portionthereof facing to the pretensioner unit 7 being walled and closed. On anedge portion of a shaft central direction of the guiding drum 21 whichis at the side of pretensioner unit 7, there is formed a flange portion27 which extends radially and outwardly from an outer peripheral portionof the guiding drum 21, roughly at a right angle with its shaft centraldirection. A clutch gear 30 is formed in an inner peripheral face ofthis flange portion 27 so that the clutch gear 30 engages the respectiveclutch pawls 29 in case of vehicle collision as will be described later.

A cylindrical mounting boss 31 is erected at a central position in theend portion of the guiding drum 21 on the pretensioner unit 7 side.Also, a drum shaft 22 formed of a steel material or the like is mountedat the central position of this end portion by press fitting or thelike. To the outer periphery of the mounting boss 31, there are fittedthe bearing 32 which has a cylindrical portion 32A having substantiallya cylindrical shape and being formed of a synthetic resin material suchas polyacetal resin or the like, and a flanged end portion 32B which isconnected at an outer periphery of a bottom end portion of thecylindrical portion 32A. The take-up drum unit 6 is rotatably supportedby a shaft receiving portion 33A of a pinion gear body 33 (refer to FIG.6 and FIG. 8) through this bearing 32. The pinion gear body 33 is formedof a steel material and the like and constitutes the pretensioner unit7.

Inside the guiding drum 21, there is formed a shaft hole 21A whichextends along a center axis thereof so as to become tapered as for thedraft angle. Within the shaft hole 21A on the flange portion 27 side,there is formed a spline groove for fitting the torsion bar 23 which ismade of a steel material or the like. The spline 23A side of the torsionbar 23 is inserted in the shaft hole 21A of the guiding drum 21 and ispress-fitted to get in contact with the flange portion 27. As a result,the torsion bar 23 is press-fitted and fixed inside the guiding drum 21so that relative rotation thereof with respect to the guiding drum 21 isdisabled.

On the locking unit 9 side in an axial direction of the guiding drum 21,there is formed a flange portion 35 which extends slightly in a radialdirection from an outer peripheral surface slightly inside an edgeportion of the guiding drum 21. Also, from an outer side of the flangeportion 35, there is formed a cylindrical stepped portion 36 of whichouter diameter of a portion at an outer side thereof becomes tapered inan axial direction. A pair of ejector pins 37 and 37 are erected atradially opposite positions in an outer end portion of the steppedportion 36.

On an outer side surface of the flange portion 35, there is formed aconvex portion in a predetermined shape. A rod-shaped wire 24 made up ofa metallic material such as a stainless steel material is mounted to anouter periphery of a bottom end portion of the stepped portion 36 so asto match the shape of this convex portion.

An outer peripheral portion of the flange portion 35 is covered by awire plate 25 which has a substantially egg-like shape in a side planview. The wire plate 25 is made of an aluminum material or the like andhas a convex portion 38 formed at an outer peripheral portion of itsinner surface facing to the guiding drum 21. The convex portion 38 isfitted with a wire 24 which protrudes outward from the flange portion35.

At a central part of the wire plate 25, there is formed a through hole40 into which the stepped portion 36 will be inserted. On an outer edgeportion of the through hole 40 at an outer side in an axial directionthereof, there are provided a pair of engaging convex portions 41 whichhave two convex portions formed thereon which protrude in a circularshape radially inwardly from an internal peripheral so as to oppose eachother in a radial direction. On an outer edge portion at an outer sidein an axial direction which is interposed between the respectiveengaging convex portions 41 of the through hole 40, there are erectedfour pairs of rivet pins 39 so as to oppose each other in a radialdirection. A concave portion 39A being recessed to a predetermined depthin a semi-circular arcuate shape is formed in a bottom end portion ofeach rivet pin 39.

A ratchet gear 26 has a cylindrical extending portion 42 having adisk-like shape and being made of a steel material or the like. Theextending portion 42 extends from an outer peripheral portion in anaxial direction up to a length substantially the same with the steppedportion 36. In an outer peripheral surface of this extending portion 42,there is formed a ratchet gear portion 45 which is engaged with the pawl43 in case of vehicle collision or vehicle emergency as will bedescribed later (refer to FIG. 9). At an edge portion of the extendingportion 42 in an axial direction on the guiding drum 21 side, there isformed a baffle flange 46 which extends from an outer peripheral portionin a radial direction. Further, a pair of engaging concave portions 46Bare provided at an outer periphery of the baffle flange 46 (refer toFIG. 5) thereon so as to oppose each other in a radial direction. Theengaging concave portions 45B each have two concave portions beingrecessed in a circular shape inwardly in a radial direction thereof.Concave portions 46A being recessed to a predetermined depth in asemi-circular arcuate shape are formed in an outer surface in the axialdirection of the baffle flange 46, so as to oppose the respective rivetpins 39.

Through holes 47 are opened in the ratchet gear 26 at positions oppositethe respective ejector pins 37 erected from the guiding drum 21 forinserting the respective ejector pins 37. Concave portions 47A beingrecessed to a predetermined depth are formed in the circumference of thethrough holes 47. A shaft portion 48 is erected at a center positionoutside of the ratchet gear 26. A spline 48A is formed at an outerperipheral surface of the shaft portion 48. The take-up drum unit 6 isthus rotatably supported by the locking unit 9 through this shaftportion 48.

A cylindrical mounting boss 49 is erected at a central part of an innersurface of the ratchet gear 26. Spline grooves are formed at an innerperipheral surface of the mounting boss 49 for fitting the spline 23Bformed at the other end of the torsion bar 23. The spline 23 B formed atthe other end of the torsion bar is formed so as to have an outerdiameter which is approximately the same as the outer diameter of thespline 23A formed at the one end of the torsion bar 23.

Accordingly, the respective engaging concave portions 46B of the baffleflange 46 in the ratchet gear 26 are fitted with the respective engagingconvex portions 41 of the wire plate 25. Thereafter, the respectiverivet pins 39 are riveted so as to expand at an inner side of theconcave portions 39A at a base end thereof and the concave portions 46Aof the baffle flange 46 formed at opposite positions. The wire 24 ismounted to an outer surface of the flange portion 35 in the guiding drum21. Next, when the wire plate 25 and the ratchet gear 26 are applied tothe outside of the flange portion 35, the spline 23B formed at the otherend of the torsion bar 23 is fitted inside the mounting boss 49 whilethe respective ejector pins 37 of the guiding drum 21 are being insertedinside the respective through holes 47 of the ratchet gear 26.Thereafter, the respective ejector pins 37 are riveted so as to beexpanded inside the concave portions 47A formed in a circumference ofthe through holes 47.

As a result, the ratchet gear 26 and the wire plate 25 are mounted sothat relative rotation thereof is disabled. This ratchet gear 26 and thewire plate 25 are also mounted to the guiding drum 21 through thetorsion bar 23 and the respective ejector pins 37 so relative rotationthereof with respect to the guiding drum 21 is disabled. The webbing 3is wound around an outer peripheral surface between the flange portion27 of the guiding drum 21 and the flange portion 35 and the wire plate25.

[Schematic Configuration of Take-Up Spring Unit]

Next, a schematic configuration of the take-up spring unit 8 will bedescribed based on FIG. 2, FIG. 4 and FIG. 5.

As shown in FIG. 2, FIG. 4 and FIG. 5, the take-up spring unit 8 has atake-up urging mechanism 55 including a spiral spring, a spring case 56for accommodating this take-up urging mechanism 55 and a spring shaft58. The take-up spring unit 8 is fixed in the respective through holes51 in the cover plate 57 constituting the outer side of the pretensionerunit 7 formed of a steel material or the like through nylon latches 8Aprovided at three locations on the spring case 56. A tip end portion ofthe drum shaft 22 in the take-up drum unit 6 is coupled with the spiralspring through the spring shaft 58 inside the spring case 56. Thus, thetake-up drum unit 6 is urged in a retracting direction of the webbing 3at all times owing to the urging force of the spiral spring.

[Schematic Configuration of Pretensioner Unit]

Next, a schematic configuration of the pretensioner unit 7 will bedescribed based on FIG. 2, and FIG. 4 through FIG. 8.

FIG. 6 is a perspective view of the pretensioner unit 7 as seen from ahousing unit 5 mounting side. FIG. 7 is a side view showing thepretensioner unit 7. FIG. 8 is an exploded perspective view showing thepretensioner unit 7 in FIG. 6 in a disassembled state.

As shown in FIG. 2, and FIG. 4 through FIG. 8, the pretensioner unit 7is comprised of a pretensioner mechanism 17 and a forced lockingmechanism 53 rotates a pawl 43 (refer to FIG. 9) which is rotatablysupported at a side wall portion 12 of the housing unit 5.

[Pretensioner Mechanism]

As shown in FIG. 5 through FIG. 8, the pretensioner mechanism 17activates a gas generating member 61 in case of vehicle collision. Thiscauses the take-up drum unit 6 to rotate in the retracting direction ofthe webbing 3 through the flange portion 27 of the take-up drum unit 6,by using the pressure of this gas.

Here, the pretensioner mechanism 17 consists of: a gas generating member61; a pipe cylinder 62; a sealing plate 63 and a piston 64 which moveinside the pipe cylinder 62 under the gas pressure from the gasgenerating member 61; a pinion gear body 33 which engages a rack formedin this piston 64 and rotates; a base plate 65, to which the pipecylinder 62 is mounted; a base block body 66 of a substantiallyrectangular shape which is in contact with the base plate 65 and mountedon a side surface of the pipe cylinder 62 on the pinion gear body 33side; and a clutch mechanism 68 provided on a back surface of the baseplate 65.

The pinion gear body 33 is provided with a pinion gear portion 71 andhas a substantially cylindrical shape on an outer peripheral portionthereof. The pinion gear body 33 is made of a steel material or the likeand engages the rack formed in the piston 64. The pinion gear body 33also has a cylinder-shaped support portion 72 formed so as to extendoutwardly from an end portion thereof on the cover plate 57 side, in anaxial direction of the pinion gear portion 71. The support portion 72 isformed to have substantially the same length as the thickness of thecover plate 57, with the root diameter of the pinion gear portion 71 asouter diameter.

A flange portion 73 extending in a radial direction is formed at an endportion of the pinion gear portion 71 on the base plate 65 side in theaxial direction thereof. Further, on the pinion gear body 33, there isformed a boss portion 74 which has a shaft receiving portion 33A formedin a substantially cylindrical-shape in an outward direction from theflange portion 73. The shaft receiving portion 33A is adapted forinserting therein the drum shaft 22 of the take-up drum unit 6 andfitting thereon the bearing 32. Three sets of splines having the outerdiameter of the bottom end portion of the boss portion 74 are formed onan outer peripheral surface of this boss portion 74 at an interval ofroughly 120° central angle.

The clutch mechanism 68 has a substantially annular-shaped pawl base 76made of a steel material or the like, three clutch pawls 29 made of asteel material or the like, and a substantially annular-shaped pawlguide 77 which is made of a synthetic resin such as polyacetal resin orthe like, and the pawl guide 77 and the pawl base 76 hold the respectiveclutch pawls 29 therebetween as will be described later.

On an inner peripheral surface of the pawl base 76 there are formedthree sets of spline grooves at an interval of roughly 120° centralangle. The spline grooves are press-fitted with the splines formed onthe boss portion 74 of the pinion gear body 33. The pawl guide 77 isformed so that an inner peripheral diameter thereof is bigger than thespline grooves in the pawl base 76. Positioning projections 77A areprovided at equal angles at three locations on the outer side face ofthe pawl guide 77 faced to the base plate 65.

The positioning projections 77A provided on the outer side face of thepawl guide 77 in the clutch mechanism 68 are engaged with thepositioning holes 81 formed in the base plate 65, to set the clutchmechanism 68 to an outer surface of the base plate 65. Next, as shown inFIG. 8, the boss portion 74 of the pinion gear body 33 is inserted intothe through hole 83 formed at substantially a central part of the baseplate 65. Thereafter, the respective splines formed on the boss portion74 is press-fitted and fixed in the respective spline grooves of thepawl base 76 constituting the clutch mechanism 68. As a result, theclutch mechanism 68 and the pinion gear body 33 are set and fixed to thebase plate 65 and the pinion gear portion 71 of the pinion gear body 33is positioned, at all times, in the position shown in FIG. 7.

The base block body 66 is made of a synthetic resin such as polyacetalresin or the like. The flange portion 73 of the pinion gear body 33 isinserted inside the through hole 82 formed on the bottom surface portionof the gear housing portion 85. This gear housing portion 85 is formedso as to be recessed in a substantially semicircle shape in plain viewin an inward direction from a side edge portion inside the base blockbody 66 and also, is formed with a bottom surface thereof protrudingoutward (refer to FIG. 11). Positioning bosses 79 protruding at a sideportion of the base block body 66 on the base plate 65 side are insertedinto the positioning holes 80 formed in the base plate 65. The baseblock body 66 is thus set to a surface of the base plate 65 (refer toFIG. 6).

An elastic engagement piece 66A is formed so as to extend from an outerside surface of the base block body 66 to the base plate 65 side andenables elastic deformation thereof in an outward direction. An elasticengagement piece 66B is formed so as to extend from a lower-side sidesurface of the base block body 66 to the base plate 65 side and enableselastic deformation thereof in an outward direction (refer to FIG. 8).The elastic engaging pieces 66A and 66B latch with the respective sideend portions of the base plate 65. As a result, the base block body 66is set to the base plate 65.

The through hole 83 formed at a substantially central portion of thebase plate 65 has an internal diameter which can support an outerdiameter of the bottom end portion of the boss portion 74 in the piniongear body 33. The through hole 83 is also formed so as to rotatablysupport the pinion gear body 33 with one end portion thereof. The gearhousing portion 85 is formed so that a height thereof is substantiallythe same as the sum of heights of the pinion gear portion 71 and theflange portion 73 in the pinion gear body 33.

[Forced Locking Mechanism]

Here, the forced locking mechanism 53 set inside the base block body 66will be described based on FIG. 5 through FIG. 8.

As shown in FIG. 7, a concave portion 86 for setting the forced lockingmechanism 53 is formed in the base block body 66. In the base block body66, there are provided a push block 87, a rotating lever 88, a blockurging spring 87A, a gear-side arm 89 and an urging spring 90, whichconstitute the forced locking mechanism 53. The block urging spring 87Aurges the push block 87 in the direction of the rotating lever 88. Theurging spring 90 urges the gear-side arm 89 in the direction of therotating lever 88. As shown in FIG. 6, to the gear-side arm 89, thereare connected a coupling shaft 91 and a mechanical arm 92 whichconstitutes the forced locking mechanism 53 from outside the base plate65.

The rotating lever 88 is made up of a synthetic resin such as polyacetalor an aluminum material or the like and is formed in a substantiallyL-shape, having through holes formed in a bending portion thereof. Asshown in FIG. 7, the rotating lever 88 is rotatably supported by a boss93 which is erected on the bottom surface of the concave portion 86provided in the base block body 66, so that one end portion of therotating lever 88 faces the pinion gear portion 71 of the pinion gearbody 33.

The push block 87 is made up of a synthetic resin such as a polyacetalresin or the like. As shown in FIG. 7, the push block 87 is positionedso that one end thereof is in the vicinity of the teeth of the piniongear portion 71 in the pinion gear body 33 and the other end thereof isin the vicinity of the rotating lever 88, by the positioning projections94 erected in a bottom surface of the concave portion 86. The push block87 is urged towards the rotating lever 88 by the block urging spring 87Aso as to prevent looseness and making noise.

Accordingly, when the pinion gear body 33 is rotated as will bedescribed later, the rotating lever 88 can be rotated in an outwarddirection (counter-clockwise direction in FIG. 7) by the push block 87which is pushed against the teeth of the pinion gear portion 71 (referto FIG. 11). The push block 87 is thus prevented from returning to thepinion gear body 33 side by the block urging spring 87A.

The gear-side arm 89 is made up of a synthetic resin such as polyacetalor the like or an aluminum material or the like and is formed in asubstantially flat plate-shape. A boss 95 to be inserted in the throughhole 96 formed in a bottom surface of the concave portion 86 in the baseblock body 66 is erected at one end portion of the gear-side arm 89which is opposite to the other portion contacting with the rotatinglever 88 at the side surface of the base block body 66. In a sidesurface onto which the boss 95 of the gear-side arm 89 is erected, thereis formed a groove portion 97 which has a predetermined depth and allowsfor insertion of a bent portion formed at one end of the coupling shaft91.

As shown in FIG. 6 and FIG. 8, the gear-side arm 89 has a steppedportion 98 formed at a tip end top surface of the rotating lever 88 soas to get in contact with the other end of the rotating lever 88. Theboss 95 of the gear-side arm 89 is inserted in the through hole 96 whichis formed at a bottom surface of the concave portion 86, and thegear-side arm 89 is rotatably supported toward the rotating lever 88side. Further, the other tip end lower side of the gear-side arm 89opposite to the stepped portion 98 is urged by the urging spring 90, andthe gear-side arm 89 is urged towards the rotating lever 88 side (upwardin FIG. 7). As a result, the stepped portion 98 will come in contactwith the other end portion of the rotating lever 88.

Accordingly, if the rotating lever 88 is rotated in a counter-clockwisedirection in FIG. 7, the other end portion of the rotating lever 88moves away from the tip end portion of the gear-side arm 89 so that thegear-side arm 89 can rotate in an outward direction (counter-clockwisedirection in FIG. 7) by the urging force of the urging spring 90.

The coupling shaft 91 is formed of a wire rod made up of a steelmaterial or the like and is bent in a substantially right angle so thatthe ends thereof face each other with approximately 90-degree of tilt.The straight portion of this coupling shaft 91 is slightly longer thanthe width of the respective side wall portions 13 and 14 (refer to FIG.9) of the housing unit 5.

As shown in FIG. 8, a groove 101 with the bent portion at one end of thecoupling shaft 91 inserted therein extends from the through hole 96formed in the bottom surface of the concave portion 86 of the base blockbody 66. A through hole 102 having a bent portion at one end of thecoupling shaft 91 inserted therein is formed at a portion facing thegear-side arm 89 of the base plate 65.

Accordingly, the bent portion at one end of the coupling shaft 91 isguided through the through hole 102 of the base plate 65, the throughhole 96 and the groove 101 of the base block body 66 to be fitted insidethe groove portion 97 of the gear-side arm 89 installed inside theconcave portion 86 of the base block body 66.

The mechanical arm 92 is made of a synthetic resin such as a polyacetalresin and the like or an aluminum material or the like and has aflat-plated and substantially fan-like shape, width of the fan-likeshape being narrow. On its outer surface of the narrower one of the endportions, there is erected a boss 106 which can be rotatably fitted inthe through hole 105 (refer to FIG. 9 and FIG. 10) formed in the sidewall portion 12 (refer to FIG. 9) of the housing unit 5. Also, a boss92A to be fitted inside a notch portion 138 (refer to FIG. 9) is erectedon an outer surface at an outer peripheral edge portion of themechanical arm 92 on the side wall portion 12 side. A groove portion 107of a predetermined depth is formed along a center line in an innersurface of the mechanical arm 92.

Accordingly, as shown in FIG. 6, the bent portion at the other end ofthe coupling shaft 91 is fitted inside the groove portion 107 of themechanical arm 92. The mechanical arm 92 is mounted to the other endside of the coupling shaft 91 so that the shaft center of the boss 106erected in the outer side surface of an edge portion at the rotationalaxis of the mechanical arm 92 and the shaft center of the coupling shaft91 become substantially straight.

If the pretensioner unit 7 is mounted to the housing unit 5 as will bedescribed later, the boss 106 of the mechanical arm 92 is rotatablyfitted inside the through hole 105 formed in the side wall portion 12(refer to FIG. 10). The boss 92A of the mechanical arm 92 is inserted inthe notch portion 138 formed in the side wall portion 12, so as to berotatably mounted inside the side wall portion 12.

[Pretensioner Mechanism]

Next, the configuration and mounting of the pipe cylinder 62constituting the pretensioner mechanism 17 will be described based onFIG. 5 through FIG. 8.

As shown in FIG. 5 through FIG. 8, the pipe cylinder 62 is formed of asteel pipe material or the like in a substantially L shape. The pipecylinder 62 has a housing portion 62A having a substantially cylindricalshape formed at one end thereof (lower-side bent portion in FIG. 7). Thepipe cylinder 62 is configured to house the gas generating member 61.This gas generating member 61 includes explosive powder which is ignitedin response to an ignition signal transmitted from a control portion notshown, generating gas as a result of gas generating agent combustion.

At the other end of the pipe cylinder 62 (top-side bent portion in FIG.7), there are formed a piston housing portion 62B having a substantiallyrectangular shape in cross section and a notch portion 111 at a portionthereof facing the pinion gear body 33. When the pipe cylinder 62 isinstalled on the base plate 65, the pinion gear portion 71 of the piniongear body 33 is fitted inside this notch portion 111. At a top endportion of the piston housing portion 62B, there is formed a notchportion 113 which is engaged with an arm portion 112 bent at asubstantially right angle from the base plate 65 at the side surfaceportion of the base block body 66 and functions as a slip-off preventionmeans of the pipe cylinder 62 in a vertical direction. A pair of throughholes 114 which are relatively opposite each other and allow insertionof a stopper screw 16 are formed at opposite side surface portions ofthe pipe cylinder 62 and sideways from the notch portion 113. Thisstopper screw 16 is used for mounting the pretensioner unit 7 to thehousing unit 5 and functions as a bounce-out prevention means of thepiston 64.

As seen in FIG. 7 and FIG. 8, the sealing plate 63 is made of a rubbermaterial or the like and formed as a substantially rectangular-shapedplate so as to allow insertion thereof from an top end portion of thepiston housing portion 62B. The sealing plate 63 has a pair ofprojecting portions 63A which extend upwards at opposite edge portionsin a longitudinal direction thereof and protrude inwardly over the fullwidth of their respective top end portions. A gas releasing hole 63B isformed at a central part in the sealing plate 63.

The piston 64 is made of a steel material or the like and has an overalllengthy shape, with a substantially rectangular shape in cross section,allowing for insertion thereof from the top end portion of the pistonhousing portion 62B. At a lower end portion of the piston 63, there areformed engagement grooves 64A wherein respective projecting portions 63Aof the sealing plated 63 are fitted from sideways. On the lower endsurface of the piston 64, there is formed a thin communicating hole 64Cwhich extends from the lower end surface of the piston 64 to a throughhole 64B formed in a side surface portion of the piston 64.

After the respective projecting portions 63A of the sealing plate 63 areslid from sideways into to engagement grooves 64A of the piston 64 forfitting therein, the sealing plate 63 is installed inside and ispress-fitted to the back side thereof in a depth direction from the topend of the piston housing portion 62B. The gas releasing hole 63B formedin the sealing plate 63 communicates with the through hole 64B throughthe communicating hole 64C of the piston 64.

Thus, in this state, the sealing plate 63 is depressed by the pressureof the gas generated in the gas generating member 61 and the piston 64is caused to move to the top end opening portion (top end portion inFIG. 7) of the piston housing portion 62B. When the webbing 3 is pulledout again after the activation of the pretensioner as will be describedlater, the piston 64 drops downward due to the reverse rotation of thepinion gear body 33. The gas inside the pipe cylinder 62 is thusreleased through the gas releasing hole 63B of the sealing plate 63, thecommunicating hole 64C and the through hole 64B of the piston 64 and thepiston 64 is caused to drop smoothly. On the side surface of the piniongear body 33 side of the piston 64, there is formed a rack 116 whichengages the pinion gear portion 71 of the pinion gear body 33. At a backsurface of a tip end portion of the rack 116 (top end portion in FIG.7), there is formed a stepped portion 117 which can come in contact withthe stopper screw 16. As shown in FIG. 7, in a normal state until thegas generating member 61 is activated, the piston 64 is positioned atthe bottom of the piston housing portion 62B and the tip end of the rack116 becomes disengaged from the pinion gear portion 71.

As shown in FIG. 7, the pipe cylinder 62 is installed on the base plate65 in such a manner that the respective projecting portions 109projecting outwardly from opposite edge portions of the gear housingportion 85 in the base block body 66 are being fitted inside the notchportion 111 of the thus configured piston housing portion 62B and thearm portion 112 of the base plate 65 is fitted inside the notch portion113 formed in the top end portion of the piston housing portion 62B. Arack locking pin 108 having a substantially U-shape in cross section iserected in the base block body 66. The rack locking pin 108 is insertedin the gear groove at the top end of the rack 116 so as to restrainvertical movement of the piston 64. The tip end portion of the piston 64is positioned in the vicinity of the pinion gear portion 71 of thepinion gear body 33, whereby the piston 64 is disengaged.

Thus, the opposite surfaces of the piston housing portion 62B in thepipe cylinder 62 are supported by ribs 110 and backrest portions 118Aand 118B. The ribs 110 have a substantially triangular shape in crosssection and are erected in a side surface of the base block body 66. Thebackrest portions 118A and 118B extend at a substantially right anglefrom portions on the side edge portions of the base plate 65 facing thepinion gear body 33. These backrest portions 118A and 118B extendslightly higher than the piston housing portion 62B and are formed so asto allow insertion thereof in the respective through holes 119A and 119Bformed at side end portions of the cover plate 57 facing the backrestportions 118A and 118B. The side edge portions of the through holes 119Aand 119B facing the outside surfaces of the backrest portions 118A and118B are recessed inwardly (leftward in FIG. 8) by a predetermined depth(for instance, approximately 1 mm deep). Thus, when the backrestportions 118A and 118B are inserted in the respective through holes 119Aand 119B, the inner surface of the through holes 119A and 119B willreliably come in contact with the outside surface of the backrestportions 118A and 118B.

With the base block body 66, the forced locking mechanism 53 and thepipe cylinder 62 etc., being installed on the base plate 65, thepositioning bosses 121 of this base block body 66 projecting in a sidesurface portion of the cover plate 57 are engaged with the respectivepositioning holes 122 of the cover plate 57. As a result, the coverplate 57 is installed on the top side of the base block body 66, theforced locking mechanism 53 and the pipe cylinder 62 etc.Simultaneously, a cylindrical support portion 72 of the pinion gear body33 is fitted in a support hole 125 formed at a substantially center partin the cover plate 57.

The backrest portions 118A and 118B which extend substantially at aright angle from the side edge portions of the base plate 65 areinserted in the respective through holes 119A and 119B formed at sideedge portions of the cover plate 57 facing the backrest portions 118Aand 118B. Elastic engagement piece 66C and elastic engagement piece 66Dare latched in the respective side end portions of the cover plate 57.The elastic engagement piece 66C extends from an outer side surface ofthe base block body 66 to the cover plate 57 side and is formed so as tobe elastically deformable outwardly. The elastic engagement piece 66Dextends from the top side surface of the base block body 66 to the coverplate 57 side and is formed so as to be elastically deformableoutwardly.

Thus, the cover plate 57 is set and fixed to the base block body 65 andthe pipe cylinder 62 is mounted between the cover plate 57 and the baseplate 65. The support portion 72 formed at the end portion of the piniongear body 33 is rotatably supported by the support hole 125 in the coverplate 57. Accordingly, as shown in FIG. 4, the support portion 72 andthe bottom end portion of the boss portion 74 formed at opposite endsportions of the pinion gear body 33 are rotatably supported by thethrough hole 83 formed in the base plate 65 and the support hole 125formed in the cover plate 57.

The through holes 114 of the pipe cylinder 62, the through hole 127formed in the cover plate 57 at a position facing the through holes 114,and the screw hole 141B formed at a position facing the through holes114 of the base plate 65 (refer to FIG. 9) are arranged coaxially. Thestopper screw 16 formed of a steel material or the like can be insertedand threaded from the cover plate 57 side towards the base plate 65side.

Accordingly, the pipe cylinder 62 is held between the cover plate 57 andthe base plate 65 and also opposite side surfaces thereof are held bythe base block body 66 and the backrest portions 118A and 118B. The topend opening of the piston housing portion 62B in the pipe cylinder 62 iscovered by a cover portion 131 which extends from the top end portion ofthe cover plate 57 at a substantially right angle therewith. The sealingplate 63 is depressed under the pressure of the gas generated by the gasgenerating member 61 and the piston 64 is caused to move toward the topend opening portion (top end in FIG. 7) of the piston housing portion62B. In this case, the stepped portion 117 of the piston 64 comes incontact with the stopper screw 16 inserted in the through holes 114 soas to stop thereat.

[Schematic Configuration of Housing Unit]

A schematic configuration of the housing unit 5 will next be describedbased on FIG. 4, FIG. 9 and FIG. 10.

FIG. 9 is an exploded perspective view of the housing unit 5. FIG. 10 isa side view showing the seatbelt retractor 1 with the locking unit 9removed therefrom.

As shown in FIG. 9 and FIG. 10, the housing unit 5 is made of a housing11, a bracket 133, a protector 135, a pawl 43 and a pawl rivet 136.

The housing 11 is made of a steel material or the like and is formed tohave a substantially U-shape in plain view. In a back-side side wallportion 12 of the housing 11, there is formed a through hole 137allowing for insertion of a tip end portion of the ratchet gear 26 inthe take-up drum unit 6. A notch portion 138 is formed at an obliquelower side of the through hole 137 at a portion facing the pawl 43 sothat the pawl 43 rotates smoothly. A through hole 139 is formed at theside of the notch portion 138 for mounting the pawl 43 in a rotatablefashion.

A semicircle-shaped guiding portion 140 is formed concentrically withthe through hole 139 at a portion of the notch portion 138 which comesin contact with the pawl 43. The portion of the pawl 43 which comes incontact with and moves along the guiding portion 140 is formed to haveapproximately the same height as the thickness of the side wall portion12. This portion has a stepped portion 43B which is recessed in acircular shape at a radius curvature which is the same as the side edgeof the guiding portion 140 and is slightly higher than the thickness ofthe side wall portion 12. As shown in FIG. 10, a guiding pin 43A iserected in a tip end portion of an outer side surface of the pawl 43.The guiding pin 43A is inserted in a guiding groove (not shown) of theclutch (not shown) constituting the locking unit 9 as will be describedlater.

As shown in FIG. 9, side wall portions 13 and 14 which are relativelyopposite to each other extend from opposite edge portions of the sidewall portion 12. Opening portions are respectively formed at a centerpart in the side wall portions 13 and 14 so as to reduce weight andimprove efficiency of the webbing mounting operation. Screwed portions13A, 13B, 14A and 14B are formed at the top and lower edge portions ofthe side wall portions 13 and 14, respectively. These screwed portionsextend inwardly by a predetermined depth, substantially at a right anglewith the respective plates. Screw holes 141A wherein the respectivescrews 15 are screwed are formed in the respective screwed portions 13A,13B and 14A by extruding. Screwed portion 141B wherein a stopper screw16 is screwed is formed in the screwed portion 14B by extruding. It isto be noted that the screwed portion may be configured to be a throughhole, through which the stopper screw 16 is inserted and fixed with anut.

A bracket 133 mounted to the top edge portion of the side wall portion13 by the respective rivets 134 is made of a steel material or the like.A horizontally long through hole 142 is formed at a portion extendingfrom the top edge portion of the side wall portion 13 in an inwarddirection at a substantially right angle therewith, for pulling out thewebbing 3 therefrom. A horizontally long frame-like protector 135 madeof a synthetic resin such as nylon or the like is fitted inside thethrough hole 142. At the lower end portion of the side wall portion 13,there is formed a bolt insertion hole 132 in which a bolt 162 (refer toFIG. 10) is inserted at the time of mounting the housing 11 to afastening piece 161 (refer to FIG. 10).

The stepped portion 43B of the pawl 43 made up of a steel material orthe like is brought in contact with the guiding portion 140 and isrotatably fixed by the rivet 136 which is inserted in a rotatablefashion from the outside of the side wall portion 12 into the throughhole 139. The side surface of the pawl 43 and the side surface of theratchet gear 26 are positioned so as to be substantially coplanar withthe outside surface of the side wall portion 12.

As shown in FIG. 10, in case the pretensioner unit 7 is mounted to thehousing unit 5 through the screws 15 and the stopper screws 16, the boss106 of the mechanical arm 92 which is mounted to the bent portion formedat the other end of the coupling shaft 91 is fitted in a rotatablefashion in the through hole 105 formed in the side wall portion 12. Theboss 106 is thus positioned in the vicinity of the lower side surface ofthe pawl 43 as positioned inside the notch portion 138. The boss 92Aerected in the outer side surface of the mechanical arm 92 is insertedin the notch portion 138. The pawl 43 will be in the vicinity of themechanical arm 92 without being engaged with the ratchet gear 26 innormal operation.

As shown in FIG. 4, FIG. 9 and FIG. 10, an arm-protective extendingportion 143 is arranged below the pawl 43 and the mechanical arm 92installed in the side wall portion 12, at a position higher than thelower end face of the side wall portion 12 by a predetermined height(for instance, approximately 10 mm). The arm-protective extendingportion 143 extends inwardly (leftward in FIG. 4) at a substantiallyright angle so as to face the pawl 43 and the mechanical arm 92 by apredetermined width (for instance, approximately 10 mm). In other words,below the pawl 43 and the mechanical arm 92 installed in the side wallportion 12, there is provided the arm-protective extending portion 143having a predetermined width which extends inwardly by a predeterminedlength (for instance, approximately 10 mm) at a substantially rightangle so as to face the mechanical arm 92.

As shown in FIG. 4, FIG. 9 and FIG. 10, a horizontally long openingportion 144A is formed in the side wall portion 13 at the position so asto face the coupling shaft 91 over substantially full length thereof.From the lower edge portion of this opening portion 144A, there isarranged a shaft-protective extending portion 144B which extendsinwardly at a substantially right angle. The shaft-protective extendingportion 144B extends so that its edge portion which is closer to theguide drum 21 is positioned deeper from the coupling shaft 91 whichfaces the side wall portion 13. Further, below this shaft-protectiveextending portion 144B, there is formed the bolt insertion hole 132through which the bolt 162 is inserted and fixed to the fastening piece161 of the vehicle with the nut 163.

[Description of Operation of Forced Locking Mechanism and Pawl]

Next, the operation of the forced locking mechanism 53 and the pawl 43when activated by the gas generating member 61 of the pretensionermechanism 17 in case of a vehicle collision will be described based onFIG. 11 and FIG. 12. FIG. 11 is an explanatory diagram showing the statethat the piston 64 is moved further in response to the activation of thegas generating member in the pretensioner mechanism 17 and the lower endportion of the rotating lever 88 is disengaged from the tip end portionof the gear-side arm 89. FIG. 12 is an explanatory diagram showing theoperation of the pawl 43 corresponding to FIG. 11.

As shown in FIG. 11, in case the gas generating member 61 of thepretensioner mechanism 17 is activated in case of a vehicle collision orthe like, the piston 64 inside the piston housing portion 62B of thepipe cylinder 62 shears the rack locking pin 108 from a normal state asshown in FIG. 7 and moves upwards (direction arrow X1) so as to causethe pinion gear body 33 rotate in a counter-clockwise direction in frontview (direction of arrow X2). As the top end portion of the rotatinglever 88 is further depressed by the push block 87 which was depressedby the block urging spring 87A, the lower end portion of this rotatinglever 88 is disengaged from the tip end portion of the gear-side arm 89.

The gear-side arm 89 is depressed in an outward direction by the urgingspring 90 and rotated in a counter-clockwise direction in front view(direction of arrow X4). The push block 87 is depressed in an outwarddirection by the block urging spring 87A to be kept disengaged from thepinion gear portion 71 of the pinion gear body 33 and makes the top endportion of the rotating lever 88 kept in contact with the internal wallsurface of the concave portion 86.

As shown in FIG. 16, in case the lower end portion of the rotating lever88 is disengaged from the tip end portion of the gear-side arm 89, thisgear-side arm 89 is rotated in a counter-clockwise direction in frontview (direction of arrow X4). This will cause the coupling shaft 91,with the bent portion formed at one end thereof being inserted insidethe groove 97 of the gear-side arm 89, to rotate in a counter-clockwisedirection as seen from a front view around a center axis (direction ofarrow X4).

As the bent portion at the other end portion of the coupling shaft 91 isinserted in the groove portion 107, the mechanical arm 92 is rotated ina counter-clockwise direction as seen from a front view (direction ofarrow X5) in response to rotation of the gear-side arm 89. This causesthe pawl 43 to engage the ratchet gear portion 45 of the ratchet gear26. The pawl 43 and the ratchet gear portion 45 of the ratchet gear 26are engaged so as to restrain rotation of the take-up drum unit 6 in thewebbing-pull-out direction and allow rotation in the retractingdirection of the webbing 3.

Accordingly, in case the pawl 43 and the ratchet gear portion 45 of theratchet gear 26 are engaged, a locking operation is carried out torestrain rotation of the take-up drum unit 6 in a pull out direction ofthe webbing 3, and rotation in the retracting direction of the webbing 3is allowed. Thus, the pawl 43 can restrain rotation of the take-up drumunit 6 in a pull out direction of the webbing 3 before the clutchmechanism 68 and the pinion gear body 33 start rotating together.

After rotation of the pinion gear body 33 is stopped followingactivation of the pretensioner mechanism 17, the lower end portion ofthe rotating lever 88 is kept away from the tip end portion of thegear-side arm 89, as shown in FIG. 15. After the pretensioner mechanism17 has been activated, the pawl 43 and the ratchet gear portion 45 ofthe ratchet gear 26 are kept engaged. Thus, the ratchet gear 26 and thewire plate 25 of the take-up drum unit 6 are restrained from rotating inthe pull out direction of the webbing 3.

As was described in detail earlier, in the seatbelt retractor 1according to the present embodiment, the side wall portion 12 of thehousing 11 is provided with, below the pawl 43 and the mechanical arm92, the arm-protective extending portion 143 which extends inwardly at asubstantially right angle. The side wall portion 13 of the housing 11 isprovided with the shaft-protective extending portion 144B which extendsinwardly at a substantially right angle from the lower edge portion ofthe horizontally long opening portion 144A which is formed so as to facesubstantially full length of the coupling shaft 91. Below thisshaft-protective extending portion 144B, there is formed the boltinsertion hole 132 through which the bolt 162 is inserted at the time ofmounting the housing 11 to the fastening piece 161 of the vehicle.

Therefore, at the time of mounting the seatbelt retractor 1 to thefastening piece 161 of the vehicle, the shaft-protective extendingportion 144B can prevent contact between the upper edge portion of thefastening piece 161 and the coupling shaft 91, and the arm-protectiveextending portion 143 can prevent contact between the upper edge portionof the fastening piece 161 and the mechanical arm 92 or the pawl 43. Asa result, it is possible to improve working efficiency of mounting theseatbelt retractor 1 to the fastening piece 161 and reliability thereof.If the gas generating member 61 of the pretensioner mechanism 17 isactivated in case of vehicle collision, the piston 64 is moved upwardsinside the piston housing portion 62B of the pipe cylinder 62 from anormal state and comes in contact with the pinion gear portion 71 of thepinion gear body 33, whereby the pinion gear body 33 is caused torotate. As a result, as the teeth of the pinion gear portion 71 in thepinion gear body 33 push the push block 87. Therefore, this push block87 shears the positioning projection 94 erected on the bottom surface ofthe base block body 66. The push block 87 which has sheared thepositioning projection 94 is pushed by the block urging spring 87A andcomes in contact with the tip end portion of the rotating lever 88,whereby the rotating lever 88 is pushed and rotated. Thus, the lower endportion of the rotating lever 88 is disengaged from the tip end portionof the gear-side arm 89. The gear-side arm 89 is thus rotated in anouter direction by the urging spring 90, and simultaneously, themechanical arm 92 is rotated through the coupling shaft 91. As a result,the pawl 43 engages the ratchet gear portion 45 of the ratchet gear 26in the take-up drum unit 6.

If the gas generating member 61 of the pretensioner mechanism 17 isactivated in case of vehicle collision, the pawl 43 is directly rotatedby the push block 87, the block urging spring 87A, the rotating lever88, the gear-side arm 89, the coupling shaft 91 and the mechanical arm92 substantially simultaneously with rotation of the pinion gear body 33by the piston 64, so as to engage the ratchet gear 26 of the take-updrum unit 6. Thus, the pawl 43 engages the ratchet gear 26 of thetake-up drum unit 6 substantially simultaneously with activation of thepretensioner mechanism 17. As a result, the take-up drum can be lockedin so as to prevent rotation thereof in the direction for the webbing 3to be pulled out swiftly and reliably, whereby the operation to pull outthe webbing 3 by vehicle occupants and a drop in the belt load can beprevented.

The present invention is not limited to the above-described embodiment,but various improvements and alterations can be made thereto withoutdeparting from the spirit of the present invention.

1. A seatbelt retractor comprising: a take-up drum onto which a webbingis wound and housed; a housing which includes a first side wall portionand a second side wall portion facing the first side wall portion, androtatably supports the take-up drum in between the first side wallportion and the second side wall portion; and a pretensioner assemblywhich rotates the take-up drum in a retracting direction to retract thewebbing in case of vehicle collision, wherein the pretensioner mechanismincludes a driving device which is mounted to an outside of the firstside wall portion of the housing and causes the take-up drum to rotatein the retracting direction of the webbing in case of the vehiclecollision, wherein the take-up drum includes: a ratchet gear formed on aperiphery of an edge portion of the take-up drum which so as to face aninside of the second side wall portion of the housing; a pawl arrangedat a position where the pawl is disengaged from the ratchet gear whileone end of the pawl is rotatably supported at the inside of the secondside wall portion of the housing; and a locking device which is directlyactivated by the driving device upon activation of the driving deviceand locks the pawl in an engaged state with the ratchet gear, whereinthe locking device, includes: an arm member one end of which isrotatably supported at an outside of the first side wall portion of thehousing; a rotating device which is provided at the outside of the firstwall portion of the housing and is directly activated by the drivingdevice so as to cause the arm member to rotate in a predetermineddirection; a depressing member which is in contact with the pawl at oneside face which is opposed to other side face thereof which is closer tothe ratchet gear while one end of the depressing member is rotatablysupported at the inside of the second wall portion of the housing; and acoupling shaft which couples the arm member and the depressing member,and wherein the housing includes: a third wall portion which is opposedto a periphery of the coupling shaft; a bolt insertion hole which isformed in an opposite end portion of the third wall portion with respectto a pull-out direction of the webbing, the bolt insertion hole beingprovided for mounting the housing to a vehicle; a first extendingportion for protecting the shaft which extends from the inside of thethird wall portion so as to be opposed to a side of the coupling shaftwhich is closer to the bolt insertion hole.
 2. The seatbelt retractoraccording to claim 1, wherein the housing includes a second extendingportion for protecting the depressing member which extends from theinside of the second side wall portion of the housing so as to protectone side face of the depressing member which is opposed to other sideface thereof which is closer to the pawl.